Clinical Manifestation of PCV2-Associated Diseases
Based on the cases submitted to the ISU-VDL, the most commonly diagnosed PCV2-associated disease problem continues to be respiratory disease as a part of the Porcine Respiratory Disease Complex (PRDC). PCV2-associated PMWS is also a major problem in the U.S. We see a substantial number of cases that we diagnose as PCV2-associated systemic infections. These are cases characterized by PCV2-associated lymphohistiocytic inflammation in a variety of tissues without evidence of lymphoid depletion. Much less commonly diagnosed diseases include PCV2-associated enteritis, abortion, and Porcine Dermatitis and Nephropathy Syndrome (PDNS). We have recently investigated a couple of outbreaks of respiratory disease and infertility in PRRSV-naïve boar studs and concluded that PCV2 played an important role along with Mycoplasma hyopneumoniae (M. hyo) and opportunistic bacteria in these cases.

Control of PCV2-Associated Diseases Summary
Until a PCV2 vaccine becomes available, our current recommendations for control of PCV2-associated diseases include the following "bullets." These are generally consistent with those recommended for implementation in eastern Canada to address recent severe outbreaks of disease (PMWS and PRDC) thought to be associated with PCV2.

• First confirm that you have a PCV2-associated problem. This will typically require doing necropsies and using other diagnostic tools. A broad menu of excellent diagnostic tools is now available.
  
• Focus on enhancing neonatal pig husbandry that will enhance colostrum uptake. Passive antibodies to PCV2 are highly protective and high levels should protect the pigs at least until they reach the finisher.
  
• Identify farm, site or system specific concurrent infections through good quality diagnostic submissions.
  
• Eliminate or minimize the effects of PRRSV coinfection if present by breeding herd stabilization, pig flow changes, and/or vaccination. Control of PRRSV will have a major impact on the outcome of PCV2 infection.
  
• Eliminate or minimize the effects of SIV coinfection if present with breeding herd and possibly pig vaccination.
  
• Determine if Porcine Parvovirus (PPV) is present in tissues of affected pigs. Consider implementing PPV vaccination of growing pigs if PPV and PCV2 coinfection is confirmed.
  
• Minimize the effect of mycoplasmal pneumonia if present with vaccination and/or strategic pulse medication.
  
• Aggressively treat specific bacterial coinfections with appropriate antimicrobials.
  
• If herd evidence suggests an association between vaccination practices and PCV2-associated disease, re-evaluate the necessity and timing of the vaccines in use. It may be beneficial to change the brand of vaccine used and/or the timing of administration of the vaccine (use of certain adjuvanted vaccines).
  
• Consider the use of increased levels of vitamin E and selenium in diets of barns experiencing PCV2-associated disease.
  
• Consider the use of enhanced diets (use of spray-dried plasma protein) on pigs that are slow to respond.
  
• Use of anti-inflammatory products such as aspirin or acetaminophen in the feed or water have reportedly been beneficial in some cases.
  
• Remove pigs that don't respond to treatment.
  
• Adhere to all-in, all-out pig flow rules.
  
• Minimize mixing and moving of pigs whenever possible.
  
• Decrease pig density.
  
• Use disinfectants in buildings and transport vehicles that have been demonstrated to be efficacious against PCV2.
  
• If it is an option, consider changing pig source/pig genetics if the problem occurs repeatedly.
  
• Monitor the status of incoming seedstock. If a substantial portion are naïve, consider appropriate acclimatization procedures such as feedback of mummified fetuses and feces or planned exposure to pigs affected with PCV2-associated diseases.
  
• Implement segregated early weaning practices and strict biosecurity to derive and maintain PCV2-free herds or flows.

References

1. Halbur P, Opriessnig T. The building blocks of PCV2-associated diseases: Cofactors, host susceptibility, strain characterization and immune modulation. In Proceedings of the AASV Preconvention Seminar #12. 37th American Association of Swine Veterinarians Annual Meeting, Kansas City, Missouri, p31-38, 2006.
   
2. Halbur P, Opriessnig T. Practical management of PCV2-associated diseases: The American experience. In Proceedings of the AASV Preconvention Seminar #12. 37th American Association of Swine Veterinarians Annual Meeting, Kansas City, Missouri, p65-71, 2006.
   
3. Cardinal F. Use of Nuflor® and Banamine® for individual treatment of PMWS and PCV2 associated pneumonia. In Proceedings of the 37th American Association of Swine Veterinarians Annual Meeting, Kansas City, Missouri, p135-137, 2006.